A Mid-Infrared Counterpart to the Magnetar 1E 2259+586

TL;DR

This paper reports the discovery of a mid-infrared counterpart to the magnetar 1E 2259+586 using Spitzer, suggesting possible dust disk or magnetospheric emission origins for its IR emission.

Contribution

First detection of a mid-infrared counterpart to 1E 2259+586, expanding understanding of magnetar IR emission mechanisms.

Findings

Mid-infrared flux density measured at 4.5 um is 6.3+/-1.0 uJy.

Infrared emission is similar to that of magnetar 4U 0142+61.

IR data can be fitted by dust disk model or power-law spectrum.

Abstract

We report the discovery of a 4.5 um counterpart to the anomalous X-ray pulsar (magnetar) 1E 2259+586 with the Spitzer Space Telescope. The mid-infrared flux density is 6.3+/-1.0 uJy at 4.5 um and <20 uJy (at 95% confidence) at 8 um, or 0.02% of the 2-10 keV X-ray flux (corrected for extinction). Combining our Spitzer measurements with previously published near-infrared data, we show that the overall infrared emission from 1E 2259+586 is qualitatively similar to that from the magnetar 4U 0142+61. Therefore the passive X-ray-heated dust disk model originally developed for 4U 0142+61 might also apply to 1E 2259+586. However, the IR data from this source can also be fitted by a simple power-law spectrum as might be expected from magnetospheric emission.